Change Android activity title from JNI call

tools/viewer/sk_app/android/surface_glue_android.cpp

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "surface_glue_android.h"
 
 #include <jni.h>
@@ skipping 13 matching lines @@
 
 namespace sk_app {
 
 static const int LOOPER_ID_MESSAGEPIPE = 1;
 
 static const std::unordered_map<int, Window::Key> ANDROID_TO_WINDOW_KEYMAP({
     {AKEYCODE_SOFT_LEFT, Window::Key::kLeft},
     {AKEYCODE_SOFT_RIGHT, Window::Key::kRight}
 });
 
-void* pthread_main(void* arg);
-
-SkiaAndroidApp::SkiaAndroidApp() {
+SkiaAndroidApp::SkiaAndroidApp(JNIEnv* env, jobject androidApp) {
+    env->GetJavaVM(&fJavaVM);
+    fAndroidApp = env->NewGlobalRef(androidApp);
     fNativeWindow = nullptr;
     pthread_create(&fThread, nullptr, pthread_main, this);
 }
 
 SkiaAndroidApp::~SkiaAndroidApp() {
+    fPThreadEnv->DeleteGlobalRef(fAndroidApp);
     if (fWindow) {
         fWindow->detach();
     }
     if (fNativeWindow) {
         ANativeWindow_release(fNativeWindow);
         fNativeWindow = nullptr;
     }
     if (fApp) {
         delete fApp;
     }
 }
 
+void SkiaAndroidApp::setTitle(const char* title) const {
+    jclass cls = fPThreadEnv->GetObjectClass(fAndroidApp);
+    jmethodID methodID = fPThreadEnv->GetMethodID(cls, "setTitle", "(Ljava/lang/String;)V");

[djsollen, 2016/05/13 15:35:58]

these JNI getters can be expensive so lookup the methodID once in the
constructor and stash it is a private variable (e.g. fSetStringMethod)

[liyuqian, 2016/05/13 16:01:00]

Done.

+    fPThreadEnv->CallVoidMethod(fAndroidApp, methodID, fPThreadEnv->NewStringUTF(title));

[djsollen, 2016/05/13 15:35:57]

this will leak the string that you just created.

jstring str = fPThreadEnv->NewStringUTF(title);
...
env->DeleteLocalRef(str);

[liyuqian, 2016/05/13 16:01:00]

Done.

+}
+
 void SkiaAndroidApp::paintIfNeeded() {
     if (fNativeWindow && fWindow) {
         fWindow->onPaint();
     }
 }
 
-void SkiaAndroidApp::postMessage(const Message& message) {
+void SkiaAndroidApp::postMessage(const Message& message) const {
     auto writeSize = write(fPipes[1], &message, sizeof(message));
     SkASSERT(writeSize == sizeof(message));
 }
 
-void SkiaAndroidApp::readMessage(Message* message) {
+void SkiaAndroidApp::readMessage(Message* message) const {
     auto readSize = read(fPipes[0], message, sizeof(Message));
     SkASSERT(readSize == sizeof(Message));
 }
 
-static int message_callback(int fd, int events, void* data) {
+int SkiaAndroidApp::message_callback(int fd, int events, void* data) {
     auto skiaAndroidApp = (SkiaAndroidApp*)data;
     Message message;
     skiaAndroidApp->readMessage(&message);
     SkDebugf("message_callback %d", message.fType);
     SkASSERT(message.fType != kUndefined);
 
     switch (message.fType) {
         case kDestroyApp: {
             delete skiaAndroidApp;
             pthread_exit(nullptr);
@@ skipping 39 matching lines @@
             break;
         }
         default: {
             // do nothing
         }
     }
 
     return 1;  // continue receiving callbacks
 }
 
-void* pthread_main(void* arg) {
+void* SkiaAndroidApp::pthread_main(void* arg) {
     SkDebugf("pthread_main begins");
 
     auto skiaAndroidApp = (SkiaAndroidApp*)arg;
 
+    // Because JNIEnv is thread sensitive, we need AttachCurrentThread to set our fPThreadEnv
+    skiaAndroidApp->fJavaVM->AttachCurrentThread(&(skiaAndroidApp->fPThreadEnv), nullptr);
+
     ALooper* looper = ALooper_prepare(ALOOPER_PREPARE_ALLOW_NON_CALLBACKS);
     pipe(skiaAndroidApp->fPipes);
     ALooper_addFd(looper, skiaAndroidApp->fPipes[0], LOOPER_ID_MESSAGEPIPE, ALOOPER_EVENT_INPUT,
                   message_callback, skiaAndroidApp);
 
     int ident;
     int events;
     struct android_poll_source* source;
 
     skiaAndroidApp->fApp = Application::Create(0, nullptr, skiaAndroidApp);
 
     while ((ident = ALooper_pollAll(-1, nullptr, &events, (void**)&source)) >= 0) {
         SkDebugf("ALooper_pollAll ident=%d", ident);
     }
 
     return nullptr;
 }
 
 extern "C"  // extern "C" is needed for JNI (although the method itself is in C++)
     JNIEXPORT jlong JNICALL
-    Java_org_skia_viewer_ViewerApplication_createNativeApp(JNIEnv* env, jobject activity) {
-    SkiaAndroidApp* skiaAndroidApp = new SkiaAndroidApp;
+    Java_org_skia_viewer_ViewerApplication_createNativeApp(JNIEnv* env, jobject application) {
+    SkiaAndroidApp* skiaAndroidApp = new SkiaAndroidApp(env, application);
     return (jlong)((size_t)skiaAndroidApp);
 }
 
 extern "C" JNIEXPORT void JNICALL Java_org_skia_viewer_ViewerApplication_destroyNativeApp(
-    JNIEnv* env, jobject activity, jlong handle) {
+    JNIEnv* env, jobject application, jlong handle) {
     auto skiaAndroidApp = (SkiaAndroidApp*)handle;
     skiaAndroidApp->postMessage(Message(kDestroyApp));
 }
 
 extern "C" JNIEXPORT void JNICALL Java_org_skia_viewer_ViewerActivity_onSurfaceCreated(
     JNIEnv* env, jobject activity, jlong handle, jobject surface) {
     auto skiaAndroidApp = (SkiaAndroidApp*)handle;
     Message message(kSurfaceCreated);
     message.fNativeWindow = ANativeWindow_fromSurface(env, surface);
     skiaAndroidApp->postMessage(message);
@@ skipping 17 matching lines @@
                                                                                    jobject activity,
                                                                                    jlong handle,
                                                                                    jint keycode) {
     auto skiaAndroidApp = (SkiaAndroidApp*)handle;
     Message message(kKeyPressed);
     message.keycode = keycode;
     skiaAndroidApp->postMessage(message);
 }
 
 }  // namespace sk_app